1. Field of the Invention
The present invention relates to a method and system for storing data using write once read many (WORM) protection including using a hardware storage device to write data to a medium wherein data is organized on the medium by block numbers, and wherein data may be written once to the medium, read many times from the medium, but not erased, modified, or overwritten.
2. Background Art
Write once read many (WORM) is a data storage technology that allows information to be written to a medium a single time and prevents the data storage device from erasing, modifying, or overwriting the data. That is, WORM describes media on which data can be written only once, data can never be overwritten, and data is intended to be read back many times. Traditionally, WORM is supported by the media itself, giving an advantage to some optical media that are physically write once, and preventing magnetic media from being used to implement WORM functionality.
WORM protection refers to the protection that prevents the user from erasing, modifying, or overwriting data on the WORM media. Optical media that is physically write once has inherent WORM protection. WORM protection also exists on VOLSAFE cartridges that are commercially available from Storage Technology Corporation, Louisville, Colo. The VOLSAFE tape cartridges have a physical/mechanical lock that prevents data overwriting when associated with a compatible drive. More specifically, the presence of the physical lock on the VOLSAFE tape is detected by specific VOLSAFE supporting drives. When the physical lock is detected, the drives prevent data overwriting. As such, VOLSAFE cartridges and compatible drives make it possible to implement WORM functionality with magnetic media.
Although WORM protection implementations that use magnetic media have been used in some applications that have been commercially successful, it is possible to counter the physical/mechanical lock. For example, physically damaging the lock or inserting the tape cartridge into a drive that does not recognize the lock could make it possible to overwrite or modify the data, overcoming the WORM protection.
For the foregoing reasons, there is a need for WORM protection of data that does not depend on a physical/mechanical lock and a compatible drive.
It is therefore an object of the present invention to provide a method and system for storing data using write once read many (WORM) protection that utilizes a WORM module external to the hardware storage device, allowing direct protection of the data itself without requiring the physical/mechanical lock and compatible drive.
In carrying out the above object, a method of storing data using write once read many (WORM) protection including using a hardware storage device to write data to a medium is provided. The data is organized on the medium by block numbers. The method further comprises establishing a write once read many (WORM) module external to the hardware storage device. A data block is received as an input to the module. A block number is specified with the module. The data block is output from the module such that the data block is written to the medium at the specified block number. The method further comprises storing the specified block number such that the specified block number is accessible to the module, and preventing future writing of data to the specified block number.
In the present invention, the write once read many (WORM) module is external to the hardware storage device. The external WORM module allows WORM protection of data by directly protecting the data itself, without depending on a physical/mechanical lock and compatible drive. The external WORM module is independent of any tape drive or cartridge, and may be implemented in software, hardware, or a combination of software and hardware. In one embodiment, the write once read many (WORM) module is established as a hardware module external to the hardware storage device. In another embodiment, the write once read many (WORM) module is established as a software module external to the hardware storage device. The software module may be implemented in a variety of ways including as part of an application programming interface (API).
Embodiments of the present invention may be implemented with different types of storage media. In one example, the storage medium is a sequential access medium. A plurality of data block is received, a plurality of block numbers is specified, and the plurality of data blocks is output such that the plurality of data blocks is written to the medium at the plurality of specified block numbers. A last specified block number of the plurality of specified block numbers is stored such that the last specified block number is accessible to the module. The module may prevent future writing of data to the plurality of specified block numbers. That is, whenever a data block is processed in the WORM module, its block number is memorized. As such, it is never possible to overwrite that block number. For sequential access storage media such as tape, because of the sequential nature of the media, only the last data block written is stored for each volume.
In another example, the storage medium is a random access medium. The plurality of specified block numbers is stored such that the plurality of specified block numbers is accessible to the module so that the module may prevent future writing of data to the plurality of specified block numbers. That is, for media that is not sequential in nature, instead of memorizing only the last data block written, all data blocks written are memorized to prevent overwriting of those block numbers.
Further, in carrying out the present invention, a system for storing data using write once read many (WORM) protection comprises a write once read many (WORM) module external to the hardware storage device. The module is programmed to receive a data block as an input to the module, specify a block number with the module, output the data block from the module such that the data block is written to the medium at the specified block number, and store the specified block number such that the specified block number is accessible to the module. The module is further programmed to prevent future writing of data to the specified block number.
The system or module may be implemented as a hardware module external to the hardware storage device or as a software module external to the hardware storage device. The software module may be implemented, for example, as part of an application programming interface (API). In addition, embodiments of the system module may be programmed for use with a sequential access medium or a random access medium so that either the last specified block number or all block numbers are memorized, as appropriate, to prevent future writing of data to previously specified and used block numbers.
Still further, in carrying out the present invention, a system for storing data using write once read many (WORM) protection is provided in combination with media including a redundant array of inexpensive tapes (RAIT). The system comprises a write once read many (WORM) module external to the hardware storage device. The module is programmed to receive a data block as an input to the module, specify a block number with the module, and output the data block from the module such that the data block is written to the media at the specified block number. The WORM module is further programmed to store the specified block number such that the specified block number is accessible to the module, and prevent future writing of data to the specified block number.
Again, the WORM module may be implemented as either a hardware module or a software module external to the hardware storage device. In addition, the software module may be implemented as, for example, part of an application programming interface (API). Because the redundant array of inexpensive tapes (RAIT) functions as a sequential access medium, the preferred implementations of the combination store a last specified block number for writing such that the last specified block number is accessible to the module so that the module may prevent future writing of data to the plurality of the specified block numbers. That is, the last block number is memorized so that it is never possible to overwrite before that block number.
The advantages associated with embodiments of the present invention are numerous. For example, methods and systems of the present invention provide WORM equipment that is independent of the storage device and storage media by implementing a WORM module as an external hardware or software module. In addition, various forms of data integrity detection techniques may be used to enforce the security of the WORM module.